The present invention relates generally to apparatus for mounting an array of pins onto an integrated circuit package and/or printed circuit board.
Integrated circuit packaging technology has significantly evolved over the past several decades to meet demands for higher I/O, I/O density and power dissipation. The foremost cause for this growth has been the need to keep pace with ever increasing levels of silicon integration.
The earliest packaging solutions relied primarily on low density xe2x80x9cpin-in holexe2x80x9d soldered interconnects where I/O counts were below 100 to 150. By the late ""70s, a new perimeter leaded package, using surface mount technology (SMT), began to gain rapid acceptance within the low I/O range. The driving force for this change was the promise of greater manufacturing efficiencies with the result being lower cost per I/O and increased placement efficiency at the board level. The 1980s saw the establishment of SMT packaging across the board for low-cost, high-volume packaging applications of under 200 I/O for the consumer, telecommunications and portable computing markets. Various forms of quad flat pack (QFP), fine pitch and small or thin outline packages were readily assembled as a strong SMT manufacturing infrastructure was developed.
At the same time, the higher I/O needs of advanced microprocessors were being met by pin grid array (PGA) packages, driven largely by the need for pluggability and pin compatibility with successive generations of processors. However, correspondingly to the higher integration, the grid of the state of the art pin grid arrays got finer as well. This caused more effort in mounting, inspecting and maintaining such connections between integrated circuit packages and circuit boards.
U.S. Pat. No. 5,742,481 discloses an intercoupling component for use with a substrate having an array of connection regions disposed on a surface of the substrate. The intercoupling component comprises an insulative support member having an upper surface and an opposite lower surface. The support member includes an array of first holes extending transversely from the upper surface to the opposite lower surface. The array of first holes is located in a pattern corresponding to the array of the connection regions. The insulative support member has a thickness between the upper and lower surfaces greater than 25% of a largest diameter of the terminal elements. The intercoupling component further comprises a plurality of terminal elements, positioned within the first holes and configured to be electrically connected to corresponding connection regions. The first holes are sized to allow the insulative support member to be slidably removed from and replaced on the terminal elements after the terminal elements are connected to the connection regions. This allows visual inspection of connections between the terminal elements and connection regions. In order to retain the socket terminals within the socket support member, the intercoupling component further includes a retaining sheet disposed over a surface of the socket support member. The retaining sheet has to be removed from the socket terminals after the socket terminals are connected to the array of connection regions to allow removal of the socket support member.
The object of the present invention is to provide an improved removable housing for mounting electrical contact elements.
The invention resides in an assembly for mounting elongated electrical contact elements onto an integrated circuit package or printed circuit board. The assembly comprises a a base plate having a first surface and a multiplicity of recesses aligned with each other in the first surface. Each of the recesses is sized and configured to receive a respective one of the contact elements. The assembly also comprises first and second spaced apart supports extending from the base plate. The assembly also comprises first and second rods received by the first and second supports and supported parallel to each other. The first and second rods define an intervening slot aligned with the recesses. The assembly also comprises a multiplicity of the contact elements. One end of each of the contact elements is received in a respective one of the recesses. The contact elements are engaged by the first and second rods, whereby the contact elements are held in their respective recesses. The rods are removable from the first and second supports to permit the contact elements to be removed from the base plate.
According to one feature of the present invention, the assembly further comprises third and fourth spaced apart supports extending from the base plate and third and fourth rods. The third and fourth rods are received by the third and fourth supports and supported parallel to each other and perpendicular to the first and second rods. The third and fourth rods define an intervening slot aligned with one of the recesses and engage the contact element in the one recess. The third and fourth rods are removable from the third and fourth supports to release the one contact element.
The electrical contact elements can be any part of an electrical plug-and-socket connection, e.g., a pin grid array socket or the respective pin terminals. The expression xe2x80x9cpin grid arrayxe2x80x9d refers to a style of integrated circuit socket or pin-out with pins laid out on a square or rectangular grid with a separation of a predefined distance in each direction.
The rods can be any straight, or almost straight, stick, shaft, bar, staff etc., of plastic, metal, or other material or a combination of different materials.
In a preferred embodiment of the present invention the first support comprises a first projection formed on a first edge of the first surface. Hence, the support member stands out from close to the border of the first surface. However, it does not necessarily have to be the farthest part from the middle of the first surface. Correspondingly, the second support member comprises a second projection formed on a second edge of the first surface basically opposite of the first edge.
According to the present invention, the first and second supports hold the rod a predetermined distance over the first surface. Even so, the rod might also be placed to touch the first surface. For that reason, the first support contains a hole extending therethrough to support a first end of the first rod. The hole is formed to allow the rod to be moved in longitudinal direction. Thus, the cross-section of the rod and that of the hole basically correspond, only the size is slightly different. The cross-section of the rod might have a round, oval, triangular, rectangular or any other shape.
Correspondingly, the second support contains a respective opening which is configured to support the other end of the rod. The hole might be formed by a recess configured to receive one tip of the rod, alternatively, it might be formed as well by a hole extending through the entire second support.
According to the present invention there are several ways the assembly is configured to enable the rod to prevent the electrical contact elements from falling out of the recesses. For example, the rod can engage a recess provided in the electrical contact elements. Alternately, the ends of the electrical contact elements in the respective recesses have a larger diameter or width than the remainder of the length of the electrical contact elements. The rods engage the electrical contact elements in their narrower region adjacent to their wider end region.
Preferably, the base plate includes a mouth on its second surface, opposite the first surface. The mouth is in the form of a funnel or cone, in order to facilitate the accessibility of the electrical contact elements, e.g., for respective contact terminals to plug into the contact elements provided in the removable housing. Advantageously, the cone shape mouth provides a large catch area for blind mating.
In a preferred embodiment of the present invention, the size of the recesses is such that the electrical contact elements loosely fit inside, i.e., the electrical contact elements are able to move slightly inside the recesses, without falling out or changing their general position. If the electrical contact elements provided in the removable housing are soldered onto a contact pad of, e.g., printed circuit board (PCB), the contact elements are automatically centered in respect to the contact pad, because of the surface tension of the melted solder material.
In a further embodiment of the mounting system, some or all of the rods are connected to each other at one end basically forming a comb where the rods form the teeth. Such an arrangement facilitates the handling of the rods and assists in taking the rods out of the assembly as a unit, when the electrical contact elements are intended to be released.
An advantage of the present invention lies in the fact that the removable housing is easy to remove or replace. This gives free access to solder joints for inspection, repair or cleaning operations. Furthermore, the removable housings and the rods or combs are reusable. Depending on the usage of the removable housing according to the present invention, they can be made of different materials. Thus, a different material might be used in a first step, when the contact elements are initially soldered onto respective connection pads. Later they can be easily exchanged by different housings of a different material.